An electronic component housing package (hereafter, a package) known in the art for housing an electronic component, such as a semiconductor device or a surface acoustic wave device, includes an insulating substrate, which is formed from sintered ceramic such as sintered aluminum oxide or sintered glass ceramic, and a recessed mount formed on the insulating substrate for housing an electronic component. The insulating substrate typically includes a rectangular flat base, and a rectangular frame body arranged on the upper surface of the base in a manner to surround the mount. The upper surface of the frame body is joined to a metal frame (also referred to as a seal ring) with a frame-shaped metallized layer and a brazing material. The upper surface of the base and the inner surfaces of the frame body and the metal frame define the recessed mount. A metal lid is joined to the upper surface of the metal frame to hermetically seal the mount (and the electronic component on the mount).
Such packages are manufactured typically using a multi-piece wiring substrate, or specifically by obtaining multiple packages collectively at a time from a single, large-area mother substrate. The multi-piece wiring substrate includes a mother substrate including multiple longitudinally and laterally arranged wiring board portions that are to be individual packages. The mother substrate is formed from, for example, sintered aluminum oxide. The mother substrate has, on its main surface, or for example on its upper surface, separation grooves formed along the boundaries of the wiring board portions. The mother substrate receives bending stress applied across the separation grooves, and then snaps and separates into individual packages. The separation grooves are cut, for example, in the upper and lower surfaces of an unfired mother substrate. Each groove is cut to a predetermined depth in the boundary between adjoining wiring board portions with a tool such as a cutter blade (refer to Japanese Unexamined Patent Application Publication No. 2006-173287).
Individual packages have become smaller recently. For example, packages fabricated recently have the dimensions of, for example, 1.6 mm by 1.2 mm or less as viewed from above. A smaller package includes a very narrow frame body, as well as a narrow portion between its mount and the external environment (a narrow frame body and a narrow metal frame) (or in other words a frame body and a metal frame each having a small distance between their outer and inner peripheries as viewed from above or having a small distance between their outer and inner side surfaces).